Realisation of a Novel Functionally Redundant Actuation System for a Railway Track-Switch

Abstract

This paper focuses on modelling, control, realisation and performance analysis of a full-scale demonstrator for a novel railway track switch. For over a century, railway track switches (or points) have been allowing trains to safely change between routes. As they are safety-critical elements of the rail network, when they fail, the signalling system will prevent trains from using that route. This means poor reliability (or lack of availability) leads to significant delays and costs; hence there is huge interest from researchers and engineers in improving the overall reliability of track switches. This paper presents new results, which represent a meaningful first step toward a revolution in the way track switches are actuated. A “REPOINT-Light” railway track switch demonstrator is introduced which uses a new concept of locking to allow redundant actuation with three actuator bearers operating under closed-loop feedback control. The new concept, its control system and its mechanical viability are tested in experiments at the Great Central Railway in the UK. To support the design of the actuators and the control system, a dynamic simulation model is developed by co-simulation involving Simulink and Simpack. The experimental results presented are used to validate the models and the paper discusses how the models themselves are used as the vehicle for the design of feedback controllers. Virtual testing of the controllers in simulation is a vital step prior to the implementation and deployment of the controllers in the demonstrator switch. The major contribution of this work is demonstrating, for the first time at full scale on a real-world track switch, that it is possible to use one-out-of-three actuator redundancy to provide fault-tolerant operation of railway track switch.

Fault-tolerant control for sensor faults affecting an electromechanical railway track switch

“…Work over a number of years culminated in both lab-scale demonstrators and a full-scale switch that was installed in a railway and could handle rolling-stock loads. 7 At its core, the REPOINT concept uses multiple actuators to replace the single one present in most operational switches. 8…”

“…Previous work by Boghani et al 3 focussed on methods to enable the design of these new mechatronic railway switches. Other work on these railway switches focussed only on closed-loop (not fault-tolerant) control 5 and full-scale testing 7 rather than fault tolerant and redundant actuation, which are the focus of this paper.…”

“…Work over a number of years culminated in both lab-scale demonstrators and a full-scale switch that was installed in a railway and could handle rolling-stock loads. 7 At its core, the REPOINT concept uses multiple actuators to replace the single one present in most operational switches. 8 With this arrangement, a more complicated control system is required to co-ordinate several feedback positioncontrol systems, rather than the more traditional 'single open-loop stall current' detection control methods.…”

Railway track switch simulation: a new dynamic model for studying actuator and switch blade dynamics

“…10 The researchers also developed a track switch model using the multi-body simulator Simpack, bending the switch track to a single actuator of a REPOINT-light switch, 11 and then a full-scale demonstrator for the novel railway track switch was built. 12 Besides, to research and design a new approach to railway track switch actuation, Dutta et al first modelled a rail unit by finite element analysis (FEA) in ABAQUS, then generated a complete switch system through Simpack, and finally linked it into Simulink to form a co-simulation space. 13 However, this kind of simulation in the co-simulation environment requires an extremely long computational time, approximately several hours to simulate one second.…”